Conventional microwave ovens are generally classified into several different types including: tabletop microwave ovens designed to be seated on a table and/or countertop; and a ventilation hood-combined microwave oven designed to be mounted above a oven range—sometimes referred to as Over-The-Range (OTR) microwaves. An OTR microwave includes a ventilation hood type system for exhausting hot air, steam, smoke, etc. generated from the oven range. The ventilation system for a typical OTR microwave normally includes a suction opening, which is frequently provided with a grease/smoke filter, located along the bottom surface of the OTR microwave. Exhaust air flow is drawn into the suction opening and is passed around the microwave oven cavity and is directed either back into the kitchen environment through an exhaust outlet opening or is directed to an external exhaust.
U.S. Pat. No. 6,433,324 discloses an exhaust flow passage system for an OTR microwave oven having an oven cavity surrounded by a outer case. In the background of this patent, various prior art systems are discussed for providing airflow passages along both sides of the microwave oven cavity and the outer case. This patent further describes and claims an OTR microwave oven having an exhaust airflow passage provided solely along one side of the oven cavity—between the oven cavity and outer case—opposite an electric equipment installation chamber.
U.S. Pat. No. 4,327,274 also discloses an OTR microwave having a bottom vent openings provided with air intake filters wherein a blower draws exhaust air in through the vent openings and directs the exhaust air through a passage between the back wall of the microwave cavity and a rear cabinet wall. The exhaust air then exits the microwave assembly through either a top or rear outlet opening, depending on the installation configuration.
U.S. Patent Application 2003/0218011 A1 discloses a wall mounted microwave oven having an exhaust fan assembly which increases an internal cooking chamber volume. This is accomplished through a fan assembly system mounted along the upper, rear corner of the microwave and which protrudes upwardly from the oven body.